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991.
A novel vanadium(IV) phosphite, (VO)(4)(4,4'-bpy)(2)(HPO(3))(4), was hydrothermally synthesized and characterized by single-crystal X-ray diffraction. This compound crystallizes in the monoclinic system with the space group C2/c and cell parameters a = 35.970(3) A, b = 15.9400(13) A, c = 10.7681(7) A, beta = 101.073(4) degrees, and Z = 8 with R(1) = 0.0482. The structure of the compound consists of trigonal bipyramidal [VO(4)N] and pseudopyramidal [HPO(3)] blocks, which are connected by corner-sharing, to form vanadium phosphite layers in the bc plane. These layers are further linked through 4,4'-bpy pillars, generating a 3D framework. Thermogravimetric analysis and magnetic susceptibility data for this compound are given. 相似文献
992.
The interaction of pinacyanol chloride(PC) with nucleic acids has been investigated by a series of experiments.Extensive hypochromism,appreciable peak shifts,isosbestic points and new peaks of the product of binding to nucleic acids in the spectra were observed.They showed that the interaction between PC and nucleic acids occurred.The results from absorption spectra of DNA,DNA melting,electrophoresis and fluorescence polarization studies have indicated that PC binds to DNA in nonintercalative way.Consistent with the nonintercalation,the studies of fluorescence titration and absorption titration specified that the binding of PC to nucleic acids occurred by an outside stacking binding,in which nucleic acids served for acting templates,The fact that the new absorption peaks of bound PC at ca,485nm are just close to the absorption bands of Haggregate of PC at high concentrations without DNA further supports the outside stacking binding mode,In addition,other evidence indicated that the interaction between PC and nucleic acids is not purely electrostatic. 相似文献
993.
Two novel 25,27-dihydroxy-26,28-bis(3-phenylthiapropxy)-calix[4]arene(3) and 25,27-dihydroxy-26,28-bis(3-phenylthiapropoxy)-5,11,17,23-tetra-tert-butylcalix[4] arene (4) were synthesized for the evaluation of their ion-selectivity in ion-selective electrodes(ISEs).ISEs based on 3 and 4 as neutral ionophores were prepared,and their selectivity coefficients for Ag^ (lg KAg,M^pot)were investigated against other alkali metal,alkaline-earth metal,aluminum,thallium(Ⅰ),Lead and some transition metal ions using the separate solution method (SSM).These ISEs showed excellent Ag^ seletivity over most of the interfering cations examined,except for Hg^2 and Fe^2 having relative smaller interference(lg KAg,M^pot≤-2.1). 相似文献
994.
The interaction of fluorocarbon containing hydrophobically modified polyelectrolyte(FMPAANa) with two kinds of nonionic surfactants(hydrogenated and fluorinated)in a semidilute (0.5wt%) aqueous solution had been studied by rheological measurements,Association behavior was found in both systems.The hydrophobic interaction of FMPAANa with fluorinated surfactant(FC171) is much stronger than that with hydrogenated surfactant(NP7.5) at low surfactoant concentrations.The interaction is strengthened by surfactants being added for the density of active junctions increased.Whereas distinct phenomena for FC171 and NP7.5 start to be found as the surfactants added over their respective certain concentration.The interaction of polyelectrolyte with fluorinated surfactant increases dramatical ly while that with hydrogenated surfactant decreases. 相似文献
995.
Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that
the reactions have two product channels: NH2+ HNCO?NH3+NCO (1) and NH2+HNCO?N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48
kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance
with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300–2700 K, transition theory rate constant
for reaction (1) is 1.68×1011–3.29×1011 mL·mol-1·s-1, which is close to the experimental one of 5.0×1011mL·mol-1·s-1or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes,cis andtrans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (forcis-mode) and 147.43 kJ/mol (fortrans-mode), respectively, which is much higher than reaction (1). So reaction (1) is the main channel for the titled reaction. 相似文献
996.
Ab initio molecular orbital calculations using the STO3-21G basis set has been carried out for the cluster series Na
n
+
, Na
n
, and Na
n
–
(wheren=2–7). The basis set is shown to be reliable compared with more extensive basis sets at the Hartree-Fock level. Thirty-one optimized structures are reported and discussed, many of which (especially for the anions) have not been considered. The STO3-21G//STO3-21G calculations suggest that for most of the species the optimum geometries are planar. In particular, the optimized structures for the anionic species should provide a starting point for more sophisticated configuration interaction calculations. 相似文献
997.
Hong Su Yi‐Hang Wen Yun‐Long Feng 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):m208-m210
The title compound, [Mn(C10H8O5S)(H2O)4]n, a one‐dimensional manganese(II) complex comprising helical chains bridged by 4‐(carboxylatomethylsulfanyl)phenoxyacetate ligands has been characterized by single‐crystal X‐ray diffraction analysis. Hydrogen‐bonding interactions between adjacent chains extend the complex into a three‐dimensional supramolecular architecture. 相似文献
998.
The reaction of alkali metal hexacyanoferrate(II/III) with (CH2)6N4 (hexamethylenetetramine, abbreviated HMT) in an acidic medium yielded crystalline compounds of stoichiometries HK2[Fe111(CN)6]·2HMT·4H2O, H2K2[Fe11(CN)6]·2HMT·4H2O, and HNa2[Fe111(CN)6]· 2HMT·5H2O. Their crystal structures are based on a packing of three molecular components: neutral and/orprotonated HMT, hexacyanoferrate, and an alkali metal ion-water cluster. The resulting three-dimensional supramolecular framework is constructed from the coordination of the alkali metal ion by aqua ligands as well as [Fe(CN)6]{n–} and HMT units, and further stabilization is achieved by hydrogen bonding between water molecules and the noncoordinated nitrogen atoms of HMT and hexacyanoferrate. 相似文献
999.
Wanlong Xiao Yuhao Mo Jing Guo Zhishan Su Shunxi Dong Xiaoming Feng 《Chemical science》2021,12(8):2940
New types of C2-symmetric chiral macrodiolides are readily obtained via chiral N,N′-dioxide-scandium(iii) complex-promoted asymmetric tandem Friedel–Crafts alkylation/intermolecular macrolactonization of ortho-quinone methides with C3-substituted indoles. This protocol provides an array of enantioenriched macrodiolides with 16, 18 or 20-membered rings in moderate to good yields with high diastereoselectivities and excellent enantioselectivities through adjusting the length of the tether at the C3 position of indoles. Density functional theory calculations indicate that the formation of macrocycles is more favorable than that of 9-membered-ring lactones in terms of kinetics and thermodynamics. The potential utility of these intriguing chiral macrodiolide molecules is demonstrated in the enantiomeric recognition of aminols and chemical recognition of metal ions.An asymmetric tandem Friedel–Crafts alkylation/intermolecular macrolactonization of ortho-quinone methides with C3-substituted indoles was achieved by using a chiral N,N′-dioxide-scandium(iii) complex. 相似文献
1000.
Zong ChunYan Gao QingYu Wang YuMei Feng JiaMin Mao ShanCheng Zhang Lu 《中国科学B辑(英文版)》2007,50(2):205-211
The ferroin-catalyzed Belousov-Zhabotinsky(BZ) reaction,the oxidation of malonic acid by acidic bromate,is the most commonly investigated chemical system for understanding spatial pattern forma-tion. Various oscillatory behaviors were found from such as mixed-mode and simple period-doubling oscillations and chaos on both Pt electrode and Br-ISE at high flow rates to mixed-mode oscillations on Br-ISE only at low flow rates. The complex dynamic behaviors were qualitatively reproduced with a two-cycle coupling model proposed initially by Gy?rgyi and Field. This investigation offered a proper medium for studying pattern formation under complex temporal dynamics. In addition,it also shows that complex oscillations and chaos in the BZ reaction can be extended to other bromate-driven nonlinear reaction systems with different metal catalysts. 相似文献